Conventional ball valves generally include a tubular valve body, a rotatable ball disposed within the center of the valve body and annular seals positioned on each side of the ball. A flow passage through the ball allows the passage of fluid when the ball is rotated into the open position. Rotating the ball to the closed position prevents fluid from passing through the ball valve.
To prevent leakage of the ball valve under high pressures, various gaskets, seal carriers or union nuts may be utilized. For example, as illustrated in U.S. Pat. No. 4,327,895, to Blumenkranz et al., a union nut is threadably attached to the valve body to retain a movable seal carrier within the ball valve housing. Annular grooves are provided within the seal carrier having an O-ring therein to prevent leakage of fluid under pressure. A disadvantage of placing the O-rings in an annular groove is that fluid may leak past the O-ring if the pressure becomes too high. Having the O-rings within a groove also requires that the O-rings be stretched over a larger diameter than the groove for placement in the groove. The O-ring may be overstretched or damaged while placing it within the groove, causing the valve to leak and requiring complete disassembly and replacement of the O-ring.